make wit_dylib::metadata public (#2456)

Previously, we only `pub use`d the `Metadata` type, but that's not terribly
useful without making all the other `pub` types in that module visible, also.

Author: dicej

crates/wit-dylib/src/lib.rs

@@ -15,7 +15,7 @@ use wit_parser::{
 
 mod async_;
 mod bindgen;
-mod metadata;
+pub mod metadata;
 pub use crate::async_::AsyncFilterSet;
 pub use crate::metadata::Metadata;